This invention relates to fluid additive supply systems for fire fighting equipment, and in particular, to systems for adding foam concentrate into a water stream used for fire fighting operations.
This application herein incorporates by reference in its entirety applications U.S. Ser. No. 09/096,798 and U.S. Ser. No. 09/284,561.
Fire fighting equipment frequently requires a mechanism that can supply an additive, such as a foam concentrate, into the equipment""s water stream. An additive, such as foam concentrate, is usually designed to be metered into a water stream at a constant percent, such as 1%, 3%, 6% of foam concentrate to water. A foam concentrate proportioning system is a system that meters, or attempts to meter, foam concentrate at a percent into a water stream. Frequently variations in flow rate of the water stream require manual adjustment of the metering system.
The instant invention relates to systems that supply additives into water streams using eduction, or a venturi device. The venturi output is connected to a conduit for fire fighting fluid. The venturi inlet can be powered by fluid from that conduit or by an independent source of fluid, such as from a separate water pump. The venturi uses fluid flow to create a pressure drop across an orifice. The pressure drop draws in or helps to drawn in additive, which additive may be at atmospheric pressure or higher pressure.
The instant invention addresses the problem of automatically metering foam concentrate into a flow of fire fighting fluid in a conduit, automatically coordinating the metering with variations in flow of the fire fighting fluid. An object of the invention is for the proportion of concentrate to fire fighting fluid to automatically remain (approximately) constant, at a preselected level, notwithstanding variations in fluid flow. A flow regulating valve for regulating flow (and/or pressure, since the two are related) of the fire fighting fluid in the conduit is utilized, which helps insure proper functioning of the venturi, together with a pilot valve to adjust the regulating valve in concert with a valve metering foam concentrate from a foam concentrate source.
The instant invention in particular can be used with a xe2x80x9cThrough the Pump Foam System,xe2x80x9d incorporated by reference to U.S. patent application Ser. No. 09/096,798 above. The instant invention represents an improvement to a Through the Pump System in that the instant invention adjusts a fire fighting fluid regulating valve and a foam concentrate source valve in response to sensed indicia of fire fighting fluid pressure (or flow) in the conduit. Said otherwise, the two valves adjust in tandem.
The Constant Pressure Drop Foam Proportioner of U.S. Ser. No. 09/593,360, also incorporated by reference herein, discloses a foam proportioning device used in association with a piston within a fluid conduit, which piston can maintain fire fighting fluid pressure at a preselected level. A pilot valve, shown both exterior to the conduit and designed within the piston in that application, serves to maintain a constant preselected pressure. As the piston varies in the fire fighting fluid conduit, in response to the pilot valve, the flow rate of the fire fighting fluid varies. As the piston varies an extension of the piston varies a foam concentrate metering orifice, supplying or feeding a venturi. Hence the piston varies fire fighting fluid flow and foam concentrate flow, in tandem.
The instant invention combines portions of a Constant Pressure Drop Foam Proportioner into a device usable in a Through The Pump Foam Systems. The instant invention improves upon prior Through The Pump Foam Systems by the fact that an additive metering valve is automatic, as in the Constant Pressure Drop Foam Proportioner. Other variations in design of the instant preferred embodiment shown, but not necessary, are the design and operation of the unit pilot valve and the design of the flow regulating valve.
The invention comprises a fire fighting fluid foam proportioning system including a fire fighting fluid conduit in fluid communication with a fire fighting fluid regulating valve and a venturi. The venturi is in fluid communication with a motive source of fluid and a valved source of fire fighting foam concentrate. A pilot valve is connected to the regulating valve and at least indirectly to the concentrate source valve. The pilot valve is adapted to adjust the regulating valve and at least indirectly the concentrate source valve in response to a sensed indicia of fire fighting fluid pressure in the conduit. The invention also includes a method for proportioning fire fighting foam concentrate comprising educting fire fighting foam concentrate into a fire fighting fluid conduit. The method includes regulating fire fighting fluid flow in the conduit in accordance with a sensed indica of fire fighting fluid pressure in the conduit and automatically metering foam concentrate to the eductor in concert with regulated fire fighting fluid flow in the conduit.